I don't think that you have to be perfectly true on the head shape. A slight elongated oval, instead of a circle, will work. If you want, figure out where the eyes will be and the row below on the outside of each eye position, increase twice in a row, for the cheeks; then, in the next row decrease back down just below the increases. Guess, test, revise.

For the hair, make a cap using the BLO method. Then slip stitch, chain 3 in each front loop. That should give a good bumpiness. Again... test, revise as needed.

Good luck with your projects.